eslint/func-style Style
What it does
Enforce the consistent use of either function declarations or expressions assigned to variables.
Why is this bad?
This rule enforces a particular type of function style, either function declarations or expressions assigned to variables. You can specify which you prefer in the configuration.
Examples
// function declaration
function doSomething() {
// ...
}
// arrow function expression assigned to a variable
const doSomethingElse = () => {
// ...
};
// function expression assigned to a variable
const doSomethingAgain = function () {
// ...
};Examples of incorrect code for this rule with the default "expression" option:
/* func-style: ["error", "expression"] */
function foo() {
// ...
}Examples of incorrect code for this rule with the "declaration" option:
/* func-style: ["error", "declaration"] */
var foo = function () {
// ...
};
var foo = () => {};Examples of incorrect code for this rule with the "declaration" and {"overrides": { "namedExports": "expression" }} option:
/* func-style: ["error", "declaration", { "overrides": { "namedExports": "expression" } }] */
export function foo() {
// ...
}Examples of incorrect code for this rule with the "expression" and {"overrides": { "namedExports": "declaration" }} option:
/* func-style: ["error", "expression", { "overrides": { "namedExports": "declaration" } }] */
export var foo = function () {
// ...
};
export var bar = () => {};Examples of correct code for this rule with the default "expression" option:
/* func-style: ["error", "expression"] */
var foo = function () {
// ...
};Examples of correct code for this rule with the "declaration" option:
/* func-style: ["error", "declaration"] */
function foo() {
// ...
}
// Methods (functions assigned to objects) are not checked by this rule
SomeObject.foo = function () {
// ...
};Examples of additional correct code for this rule with the "declaration", { "allowArrowFunctions": true } options:
/* func-style: ["error", "declaration", { "allowArrowFunctions": true }] */
var foo = () => {};Examples of correct code for this rule with the "declaration" and {"overrides": { "namedExports": "expression" }} option:
/* func-style: ["error", "declaration", { "overrides": { "namedExports": "expression" } }] */
export var foo = function () {
// ...
};
export var bar = () => {};Examples of correct code for this rule with the "expression" and {"overrides": { "namedExports": "declaration" }} option:
/* func-style: ["error", "expression", { "overrides": { "namedExports": "declaration" } }] */
export function foo() {
// ...
}Examples of correct code for this rule with the {"overrides": { "namedExports": "ignore" }} option:
/* func-style: ["error", "expression", { "overrides": { "namedExports": "ignore" } }] */
export var foo = function () {
// ...
};
export var bar = () => {};
export function baz() {
// ...
}Configuration
The 1st option
type: "expression" | "declaration"
The 2nd option
This option is an object with the following properties:
allowArrowFunctions
type: boolean
default: false
When true, arrow functions are allowed regardless of the style setting.
allowTypeAnnotation
type: boolean
default: false
When true, functions with type annotations are allowed regardless of the style setting.
overrides
type: object
Override the style specifically for named exports. Can be "expression", "declaration", or "ignore" (default).
overrides.namedExports
type: "ignore" | "expression" | "declaration"
default: null
How to use
To enable this rule using the config file or in the CLI, you can use:
{
"rules": {
"func-style": "error"
}
}import { defineConfig } from "oxlint";
export default defineConfig({
rules: {
"func-style": "error",
},
});oxlint --deny func-styleVersion
This rule was added in v0.15.11.